1 Leaves palmately divided (if 1-ternate, then palmately so, the terminal leaflets on a petiolule the same length as the those of the lateral leaflets); [“Dentaria”].

  2 Plants entirely glabrous (including on the leaf margins); leaflets highly dissected with linear to filiform segments

    3 Leaf segments > 10 per leaf, each usually sublobed or toothed

    3 Leaf segments < 7 per leaf, each linear, or some of them bifurcate into 2 equal or unequal lobes

  2 Plants with marginal leaf trichomes, and often also pubescent on the stem, inflorescence, and petioles; leaflets entire, toothed, or deeply lobed.

      4 Trichomes of leaf margins appressed and ca. 0.1 mm long; stem leaves 2 (-3), opposite; lateral leaflets of stem leaves very rarely incised, the leaf being (and appearing merely 3-foliolate, though teeth may be prominent and lacerate); basal leaves usually present at flowering.

        5 Rhizome with 2-3 cm long segments, each separated by a narrow and fragile connecting portion (which typically is broken on herbarium specimens), and lacking “teeth” (actually prominent reduced leaves); leaflets of the stem leaves (2.5×-) avg. 5× (-7×) as long as wide (thus proportionately much narrower than the leaflets of the basal leaves); central leaflet of stem leaves (2.5-) avg. 3.25 (-4) cm long × (0.5-) avg. 0.75 (-1.0) cm wide; taste of fresh plant relatively mildly mustardy

        5 Rhizome elongate and of uniform diameter, lacking definite segments, but with periodic “teeth” (prominent reduced leaves) along it; leaflets of the stem leaves (2×-) avg. 3× (-4×) as long as wide (thus proportionately similar to the leaflets of the basal leaves); central leaflet of stem leaves (4-) avg. 6 (-8) cm long × (1.5-) avg. 2 (-2.5) cm wide; taste of fresh plant strong, like horseradish or wasabi

      4 Trichomes of leaf margins erect and 0.2-0.3 mm long; stem leaves 3, whorled; lateral leaflets of stem leaves usually incised into 2 main lobes, giving the leaf a superficially somewhat 5-parted appearance; basal leaves usually absent (or often present in C. maxima) at flowering.

          6 Rhizome with 2-3 cm long segments, each separated by a narrow and fragile connecting portion (which typically is broken on herbarium specimens); upper stem pubescent

          6 Rhizome elongate, with alternating thicker and thinner portions (but not fragile and easily separating); upper stem glabrous

1 Leaves simple, pinnately lobed, or pinnately divided (if 1-ternate, then pinnately so, the terminal leaflet on a longer petiolule than those of the lateral leaflets); [Cardamine in the narrow sense].

             7 Cauline leaves simple, sometimes the lower to middle cauline leaves with 1-2 pairs of very small lateral lobes.

               8 Plant from a tuberous or bulbous base, erect and generally unbranched, not stoloniferous or rooting down from upper nodes after flowering; petals 7-20 mm long.

                 9 Stem glabrous, or with hairs < 0.1 mm long; corolla white, rarely pink; stem leaves 4-12; silique 1.5-3 cm long, plus a 3-7 mm beak

               8 Plant from a fibrous root system, frequently much branched from the base, some of the branches becoming stoloniferous and rooting down at the upper nodes after flowering; petals 2-10 mm long or absent.

                   10 Petals absent or present, if present 0.7-2 mm long; silique 5-10 (-15) mm long, plus a 0.5-1.0 mm beak, on thick pedicels 1-3 (-6) mm long

                   10 Petals present, 2-10 mm long; silique 8-21 mm long, plus a 1-3 mm beak, on slender pedicels 10-20 mm long.

                     11 Petals 3-5 mm long, the tips ascending or erect; anthers orbicular, ca. 0.3 mm across; stylar beak of the silique 1-1.5 mm; mid-cauline and upper cauline leaves cuneate, rounded, or truncate (rarely the mid-cauline leaves subcordate, but not clasping); basal leaves with 1-3 pairs of lateral leaflets

                     11 Petals 5-10 mm long, the tips spreading or ascending; anthers oblong, about 1 mm long; stylar beak of the silique 2-3 mm; mid-cauline and upper cauline leaves cordate, often clasping around the stem or branch; basal leaves with 0-1 pairs of lateral leaflets

             7 Cauline leaves 1-ternate or pinnatifid (if 1-ternate, the lateral leaflets about as large as the terminal leaflet).

                       12 Cauline leaves with 3-5 leaflets; petals 4-10 mm long; plant a perennial.

                          13 Stem glabrous at base; lower leaves green underneath; petioles auriculate at the base, the auricles 1-5 mm long, acute to acuminate; leaves 3 (-5)-foliolate; siliques 22-40 mm long

                          13 Stem pubescent at base; lower leaves purple underneath; petioles not auriculate at the base; leaves 3-5-foliolate; siliques 10-25 mm long.

                       12 Cauline leaves with 7-numerous leaflets; petals 1-4 mm long or absent (8-15 mm long in C. pratensis); plant an annual, biennial, or perennial.

                            14 Petals 8-15 mm long.

                              15 Petals white; leaflets of upper stem leaves petiolulate

                              15 Petals pink; leaflets of upper stem leaves sessile, often decurrent on the rachis

                            14 Petals 1-4 mm long or absent.

                                16 Cauline leaves with prolonged sagittate-auriculate bases, the 13-19 leaflets acuminate

                                16 Cauline leaves without basal auricles, the 5-15 (-17) leaflets mostly obtuse.

                                  17 Stamens 4 (rarely 5 or 6); plant with many, persistent basal leaves forming a compact rosette; stem bases and petioles hirsute

                                  17 Stamens 6; plant with few or no basal leaves, not forming a rosette or forming a loose rosette; stem bases and petioles glabrous (or sparsely hirsute).

                                    18 Cauline leaves 2-4 cm long; terminal leaflet similar to the lateral leaflets in size and shape; leaflets neither decurrent along the rachis nor petiolulate; stem glabrous throughout

                                    18 Cauline leaves 4-10 cm long; terminal leaflet broader than the lateral leaflets; leaflets either decurrent along the rachis or petiolulate; stem pubescent at base.

                                       19 Leaflets decurrent on the rachis; stems typically erect; [native]

                                       19 Leaflets petiolulate; stems flexuous; [exotic weed].

                                         20 Middle stem leaflets strikingly hairy on the upper surface; basal leaves forming a rosette; stem markedly hairy; terminal leaflet of the middle stem leaf 1-7 (-9) lobed with both deep and shallow sinuses; petals <2× as wide as the sepals

                                         20 Middle stem leaflets predominantly glabrous on the upper surface; basal leaves not forming a rosette; stem hairy or glabrous basally, glabrous or rarely sparsely hairy in the upper part; terminal leaflet of the middle stem leaf (1-) 3-5 (-7) lobed with deep and sharp sinuses; petals >2× as wide as the sepals